1. Field of the Invention
The present invention relates to a process for producing glutathione. More specifically, it relates to a process which comprises cultivating a mutant strain of the genus Saccharomyces which is resistant to 1,2,4-triazole and/or sodium azide in a culture medium to accumulate large amounts of glutathione in the microbial cells and recovering the glutathione.
Glutathione, a tripeptide which takes part in an oxidation-reduction system in the living body, is useful as a medicine for strengthening liver functions, detoxification, and so forth.
2. Description of Prior Art
As industrial process for producing glutathione, synethetic processes, processes for extraction from yeasts, and so forth, have already been reported; however, the synthetic processes involve complicated steps for synthesizing the L-isomer having physiological activities, and the extraction from yeast cells, which affords only the L-isomer, has a defect that the yield is low.
As improved methods, there have been reported a process in which L-cysteine, a precursor of glutathione, alone or in combination with glutamic acid or glycine is added to the medium to increase the glutathione content of cells (Japanese Published Unexamined Patent Application Nos. 44488/1973, 92579/1973, 156994/1977 and 94089/1978), a process in which methionine or L-cystine is added to the medium to increase the glutathione content of cells (Japanese Published Unexamined Patent Application Nos. 22685/1973, 44487/1973, 139685/1976 and 156994/1977), and so forth. In addition, as methods employing improved yeasts, a process in which an L- or DL-ethionine-sensitive strain of Candida utilis is employed (Japanese Published Unexamined Patent Application No. 87296/1977), a process in which an ethionine-resistant strain of Candida utilis is employed (Japanese Published Unexamined Patent Application No. 125687/1977), and so forth, are known.
The production yields of such processes are comparatively low from a commercial application standpoint. Thus, a need exists for a process for producing glutathione in higher yields at low cost.
To this end, it has now been found that glutathione productivity of a glutathione-producing microorganism belonging to the genus Saccharomyces is greatly improved when such microorganism is endowed with a resistance to 1,2,4-triazole or sodium azide.
Heretofore, it was not recognized that the productivity of glutathione could be improved by endowing a glutathione-producing microorganism with either of such traits.